180mTa excitation by positrons

For the first time the 180mTa excitations cross-sections have been measured at the photonless annihilation of the positrons. The effective cross-sections have been obtained: σef(180mTa) = (4.0 ± 1.0) x 10-25 cm2, and σef(180mTa) = (1.7 ± 0.3) x 10-27 cm2 for the end point energies of the positrons about: 3.9 and 1.0 MeV, accordingly. From the effective cross-sections, the differential cross-sections σph have been calculated. The value of the differential cross sections considerably differs from the existing theoretical calculations. The comparison of the integral cross-sections dependence both the photonless annihilation and (γ γ')-reaction with Bremsstrahlung photons from energy was done. The correlation of the experimental data was shown.